Electrical and Electronic Engineering - Theses
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ItemSignal processing for optical performance monitoring and impairment mitigation( 2006)Optical performance monitoring is essential for managing optical networks. One important quantity to monitor is the optical signal-to-noise ratio (OSNR). And in high bit rate fiber optical systems operating at 10 Gb/s or beyond, compensating optical impairments becomes important. In this thesis, we investigate OSNR monitoring using beat noise and present two new OSNR monitoring techniques. We propose an OSNR monitoring technique using uncorrelated beat noise and show by experiment for a 10 Gb/s system that in the OSNR range from 10 dB to 30 dB, the proposed OSNR monitoring scheme has a measurement error of less than 0.5 dB. Then, we propose and experimentally demonstrate for the first time an OSNR monitoring technique using beat noise for optical packet switched networks which performs monitoring on a packet basis. The response time of the OSNR monitor can be around 10 ns and the OSNR measurement error is found to be less than 0.6 dB for OSNR from 10 dB to 30 dB. We also explore chromatic dispersion and polarization-mode dispersion (PMD) mitigation using Viterbi equalization in 10 Gb/s nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) and differential quadrature phase-shift keying (NRZ-DQPSK) systems. We show through simulations that using Viterbi equalizers improves the performance of NRZ-OOK, NRZ-DPSK and NRZ-DQPSK receivers. For NRZ-DQPSK receiver with a Viterbi equalizer, the chromatic dispersion tolerance is about 5048 ps/nm and the PMD tolerance is about 160 ps at 3 dB OSNR penalty.